1. Field of the Invention
The present invention relates to a feed mechanism for taking out one of a plurality of sheets of recording paper that are stacked and transferring that one sheet, and a recording apparatus including such a feed mechanism.
Moreover, the present invention relates to a liquid ejection device such as an ink-jet recording apparatus, which has the above feed mechanism and performs liquid ejection onto a medium by emitting liquid such as ink, from its head.
The liquid ejection apparatus in the present application means a recording apparatus which uses an ink-jet type recording head and achieves printing on the recording medium by emitting ink from the recording head, such as a printer, a copier and a facsimile machine, as well as an apparatus which uses a liquid ejection head corresponding to the ink-jet type recording head and emits liquid suitable for an application of the apparatus in place of the ink from the ink ejection head to a medium, thereby causing the liquid to adhere to the medium.
Examples of such a liquid ejection head include a color-material ejection head used in fabrication of color filters for a liquid crystal display or the like, an electrode-material (conductive paste) ejection head used in formation of electrodes for an organic EL display or a field emission display (FED), a biological organic material ejection head used in fabrication of bio-chips, and a sample ejection head as a precise pipette, other than the aforementioned recording head.
2. Description of the Related Art
Conventionally, there are known various structures for preventing simultaneous transfer of two or more sheets of paper in a feed mechanism, as described in Japanese Patent Applications Laying-Open Nos. 2002-332130 and 2003-26349, for example.
According to the structure described in Japanese Patent Application Publication No. 2002-332130, in order to provide sheet feed mechanism that does not cause the increase of the size of the device and the large increase of the cost and includes a simultaneous-transfer preventing mechanism having a simple structure, a lever protrusion extending from one end face of a rotation shaft that is formed integrally with are turn lever is inserted into a concave arc-shaped notch formed in a control cam, in such a manner that the lever protrusion can move within that notch in a radial direction. By the contact of this lever protrusion with the first contact face and second contact face of the notch, a relative rotation angle between the rotation shaft and the control cam is limited. While a feed operation has been completed yet and a trailing end of a sheet remains inside the sheet feed mechanism after a part in the main body of a recording apparatus or the like holds that sheet, that sheet pushes the return lever to rotate it toward a particular direction, thereby moving the return lever away from a transfer path of the sheet.
On the other hand, Japanese Patent Application Publication No. 2003-26349 discloses the following structure in order to prevent the simultaneous transfer without using a complicated mechanism or control, as well as the increase of the time required for the feed operation. In this operation, a return-lever control cam for driving the return lever follows a cam provided to an ASF control gear moving in conjunction with a feed roller, thereby causing the return lever to operate in conjunction with the feed roller. At the first position, the return lever enters into a path through which a sheet is passing, thereby preventing the top end of that sheet from improperly entering the inner region of the feed mechanism when that sheet is set. The return lever returns the leading end of the sheet newly placed to a predetermined sheet-top reference position by rotating from the first position to the second position. At the third position, the return lever is moved away so as not to disturb a sheet-separation operation and a transfer operation.
In recent years, a small printer for performing printing onto a postcard or a business card has been developed. Thus, the size of the feeding device used in such a small printer also becomes smaller. However, if the return lever mentioned in the description of the above conventional techniques, i.e., the return lever for returning the sheet simultaneously transferred with the sheet to be transferred to the sheet-holding portion is reduced in size, i.e., is shortened, the effect of the return lever cannot be achieved sufficiently. However, if the size of the feed mechanism is reduced while keeping the return lever unchanged, the top end of the return lever passes through an inner position than the outer circumferential surface of the feed roller when the return lever rotates. Thus, the top end of the return lever brings a part of the sheet up from the rear side of the sheet, causing irregularity of the sheet.